Special thanks to Audrey Wong, Principal Technical Artist, Pixar Animation Studios, for providing this link to a technical paper authored by Theodore Kim, Fernando de Goes, and Hayley Iben, describing technologies used to create Hank the octopus in "Finding Dory." Some of these technologies were later incorporated into SideFX's Houdini software and Vellum. Unlike Cinema 4D, which uses quadrangles and N-gons, Houdini employs tetrahedrons to create meshes. 

https://graphics.pixar.com/library/AnisotropicElasticitySIGGRAPH2019/paper.pdf
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A test animation of one tentacle, using dynamics. 

The arms have been welded on. A tedious task, since it involves vertices on all eight arms, but no more tedious than dealing with suckers. 

The first rigged arm was cloned in mograph. Using Current State to Object, seven duplicates were made. Each "shoulder" has ten vertices that match the ten vertices at the end of each arm, so welding the points together should go relatively smoothly. Suckers crossed.

I'm correcting and tweaking the mesh prior to rigging. Here I've placed the head and shoulders portion in a cloth surface to give the model thickness. From there I used the Fit Circle command to make eight individual circular edges so I can connect the tentacles to what is now the body. And for those who got this far in the post and are thinking about lunch or dinner choices, I recommend the Margherita pie at Joe's Pizza in Santa Monica and West Hollywood. It has a sweet flavor and is arguably the best pizza in Los Angeles. Just saying.

Creating a vertex map to keep the suckers from deforming when zremesher is applied.

Summer is almost here--one day away, in fact--so just in the nick of time for a spring shower render, as we bid adieu to an old bathroom in great need of an overhaul.

The word "tentacles" always reminds me of the 1977 "Jaws" quickie that somehow managed to attract Henry Fonda, John Huston and Shelley Winters to its cast, not to mention a very talented octopus who is often shot in close-up. Director Ovidio Assonitis (credited as "Oliver Hellman") later worked with James Cameron on "Piranha II: The Spawning," but who directed what on that movie remains a mystery to this day, perhaps for good reason.

On to making my own tentacles which, thanks to the magic of mograph, have more suckers than a bitcoin convention.

I added eyeballs to the sockets and rigged them to move in unison using a single controller. I also did a quick render of the head using a modified CGAxis texture to see how things are coming along.